Electrical gradients in water can create risks of electrocution and electroshock drowning if an individual enters water in which a sufficiently strong voltage gradient is present. Such hazardous conditions can occur in swimming pools, hot tubs, spas, and Jacuzzis which have improperly installed, poorly maintained, or otherwise faulty underwater lighting, heaters pumps, wiring, or other electrically operated equipment or appliances. Currently, protection against electrocution and electroshock drowning hazards in such facilities depends mainly upon the use of GFCI (ground fault circuit interrupter) circuit breakers being installed on AC power lines. However, such circuit breakers may not be present in older facilities, which are also subject to greater risk due to deterioration over time of wiring for underwater equipment. There are also possibilities of risk at locations in more open water, where voltage gradients may be present due to fallen electrical transmission lines, current leakage from boats, or other voltage sources.
One device that has been developed for providing an indication of AC voltage gradient strength in seawater is the Voltage Gradient Probe marketed by Online Electronics Ltd. of Aberdeen, Scotland, UK. This device is described as a hand-held, subsea unit for providing an easily interpreted indication of AC electric field strength in seawater to indicate to divers or ROVs the presence of any local AC electric fields while working on subsea electrical equipment. The device appears to be limited to active use, and detects only AC voltages. Furthermore, the device is described as having a typical battery life of 10 days, making it ill-suited for passively monitoring a location to provide warning of when a voltage gradient is present in the water at that location.
A less critical risk is caused by voltage gradients that cause increased corrosion of vessels or other equipment that are immersed in water where such a gradient is present. Such gradients can greatly accelerate damage due to electrolytic corrosion or galvanic corrosion, and thus detecting such gradients is of particular interest to operators of marinas and other areas where vessels are present.